encoding: Add bitvec based write_packet_uplink_ack
The current write_packet_uplink_ack implementation is based on the
CSN.1 encoder which makes it difficult to do the bitmap encoding for
EGPRS.
Add a new implementation based on bitvec functions to create the
PACKET UPLINK ACK/NACK messages.
Sponsored-by: On-Waves ehf
diff --git a/src/encoding.cpp b/src/encoding.cpp
index 6d66a72..4cbcd8c 100644
--- a/src/encoding.cpp
+++ b/src/encoding.cpp
@@ -516,6 +516,182 @@
}
}
+static void write_packet_ack_nack_desc_gprs(
+ struct gprs_rlcmac_bts *bts, bitvec * dest, unsigned& wp,
+ gprs_rlc_ul_window *window, bool is_final)
+{
+ char rbb[65];
+
+ window->update_rbb(rbb);
+
+ rbb[64] = 0;
+ LOGP(DRLCMACUL, LOGL_DEBUG, "- V(N): \"%s\" R=Received "
+ "I=Invalid\n", rbb);
+
+ bitvec_write_field(dest, wp, is_final, 1); // FINAL_ACK_INDICATION
+ bitvec_write_field(dest, wp, window->ssn(), 7); // STARTING_SEQUENCE_NUMBER
+
+ for (int i = 0; i < 64; i++) {
+ /* Set bit at the appropriate position (see 3GPP TS 04.60 9.1.8.1) */
+ bool is_ack = (rbb[i] == 'R');
+ bitvec_write_field(dest, wp, is_ack, 1);
+ }
+}
+
+static void write_packet_uplink_ack_gprs(
+ struct gprs_rlcmac_bts *bts, bitvec * dest, unsigned& wp,
+ struct gprs_rlcmac_ul_tbf *tbf, bool is_final)
+{
+
+ bitvec_write_field(dest, wp, tbf->current_cs() - 1, 2); // CHANNEL_CODING_COMMAND
+ write_packet_ack_nack_desc_gprs(bts, dest, wp, &tbf->m_window, is_final);
+
+ bitvec_write_field(dest, wp, 1, 1); // 1: have CONTENTION_RESOLUTION_TLLI
+ bitvec_write_field(dest, wp, tbf->tlli(), 32); // CONTENTION_RESOLUTION_TLLI
+
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have Packet Timing Advance
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have Power Control Parameters
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have Extension Bits
+ bitvec_write_field(dest, wp, 0, 1); // fixed 0
+ bitvec_write_field(dest, wp, 1, 1); // 1: have Additions R99
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have Packet Extended Timing Advance
+ bitvec_write_field(dest, wp, 1, 1); // TBF_EST (enabled)
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have REL 5
+};
+
+static void write_packet_ack_nack_desc_egprs(
+ struct gprs_rlcmac_bts *bts, bitvec * dest, unsigned& wp,
+ gprs_rlc_ul_window *window, bool is_final)
+{
+ int urbb_len = 0;
+ int crbb_len = 0;
+ int len;
+ bool bow = true;
+ bool eow = true;
+ int ssn = window->mod_sns(window->v_q() + 1);
+ int num_blocks = window->mod_sns(window->v_r() - window->v_q());
+ int esn_crbb = window->mod_sns(ssn - 1);
+ int rest_bits = dest->data_len * 8 - wp;
+
+ if (num_blocks > 0)
+ /* V(Q) is NACK and omitted -> SSN = V(Q) + 1 */
+ num_blocks -= 1;
+
+ if (num_blocks > window->ws())
+ num_blocks = window->ws();
+
+ if (num_blocks > rest_bits) {
+ eow = false;
+ urbb_len = rest_bits;
+ /* TODO: use compression, start encoding bits and stop when the
+ * space is exhausted. Use the first combination that encodes
+ * all bits. If there is none, use the combination that encodes
+ * the largest number of bits (e.g. by setting num_blocks to the
+ * max and repeating the construction).
+ */
+ } else if (num_blocks > rest_bits - 9) {
+ /* union bit and length field take 9 bits */
+ eow = false;
+ urbb_len = rest_bits - 9;
+ /* TODO: use compression (see above) */
+ }
+
+ if (urbb_len + crbb_len == rest_bits)
+ len = -1;
+ else if (crbb_len == 0)
+ len = urbb_len + 15;
+ else
+ len = urbb_len + crbb_len + 23;
+
+ /* EGPRS Ack/Nack Description IE */
+ if (len < 0) {
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have length
+ } else {
+ bitvec_write_field(dest, wp, 1, 1); // 1: have length
+ bitvec_write_field(dest, wp, len, 8); // length
+ }
+
+ bitvec_write_field(dest, wp, is_final, 1); // FINAL_ACK_INDICATION
+ bitvec_write_field(dest, wp, bow, 1); // BEGINNING_OF_WINDOW
+ bitvec_write_field(dest, wp, eow, 1); // END_OF_WINDOW
+ bitvec_write_field(dest, wp, ssn, 11); // STARTING_SEQUENCE_NUMBER
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have CRBB
+
+ /* TODO: Add CRBB support */
+
+ LOGP(DRLCMACUL, LOGL_DEBUG,
+ " - EGPRS URBB, len = %d, SSN = %d, ESN_CRBB = %d, "
+ "SNS = %d, WS = %d, V(Q) = %d, V(R) = %d%s%s\n",
+ urbb_len, ssn, esn_crbb,
+ window->sns(), window->ws(), window->v_q(), window->v_r(),
+ bow ? ", BOW" : "", eow ? ", EOW" : "");
+ for (int i = urbb_len; i > 0; i--) {
+ /* Set bit at the appropriate position (see 3GPP TS 04.60 12.3.1) */
+ bool is_ack = window->m_v_n.is_received(esn_crbb + i);
+ bitvec_write_field(dest, wp, is_ack, 1);
+ }
+}
+
+static void write_packet_uplink_ack_egprs(
+ struct gprs_rlcmac_bts *bts, bitvec * dest, unsigned& wp,
+ struct gprs_rlcmac_ul_tbf *tbf, bool is_final)
+{
+ bitvec_write_field(dest, wp, 0, 2); // fixed 00
+ bitvec_write_field(dest, wp, 2, 4); // CHANNEL_CODING_COMMAND: MCS-3
+ // bitvec_write_field(dest, wp, tbf->current_cs() - 1, 4); // CHANNEL_CODING_COMMAND
+ bitvec_write_field(dest, wp, 0, 1); // 0: no RESEGMENT (nyi)
+ bitvec_write_field(dest, wp, 1, 1); // PRE_EMPTIVE_TRANSMISSION, TODO: This resembles GPRS, change it?
+ bitvec_write_field(dest, wp, 0, 1); // 0: no PRR_RETRANSMISSION_REQUEST, TODO: clarify
+ bitvec_write_field(dest, wp, 0, 1); // 0: no ARAC_RETRANSMISSION_REQUEST, TODO: clarify
+ bitvec_write_field(dest, wp, 1, 1); // 1: have CONTENTION_RESOLUTION_TLLI
+ bitvec_write_field(dest, wp, tbf->tlli(), 32); // CONTENTION_RESOLUTION_TLLI
+ bitvec_write_field(dest, wp, 1, 1); // TBF_EST (enabled)
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have Packet Timing Advance
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have Packet Extended Timing Advance
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have Power Control Parameters
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have Extension Bits
+
+ write_packet_ack_nack_desc_egprs(bts, dest, wp, &tbf->m_window, is_final);
+
+ bitvec_write_field(dest, wp, 0, 1); // fixed 0
+ bitvec_write_field(dest, wp, 0, 1); // 0: don't have REL 5
+};
+
+void Encoding::write_packet_uplink_ack(
+ struct gprs_rlcmac_bts *bts, bitvec * dest,
+ struct gprs_rlcmac_ul_tbf *tbf, bool is_final)
+{
+ unsigned wp = 0;
+
+ LOGP(DRLCMACUL, LOGL_DEBUG, "Encoding Ack/Nack for %s "
+ "(final=%d)\n", tbf_name(tbf), is_final);
+
+ bitvec_write_field(dest, wp, 0x1, 2); // Payload Type
+ bitvec_write_field(dest, wp, 0x0, 2); // Uplink block with TDMA framenumber (N+13)
+ bitvec_write_field(dest, wp, is_final, 1); // Suppl/Polling Bit
+ bitvec_write_field(dest, wp, 0x0, 3); // Uplink state flag
+ bitvec_write_field(dest, wp, 0x9, 6); // MESSAGE TYPE Uplink Ack/Nack
+ bitvec_write_field(dest, wp, 0x0, 2); // Page Mode
+
+ bitvec_write_field(dest, wp, 0x0, 2); // fixed 00
+ bitvec_write_field(dest, wp, tbf->tfi(), 5); // Uplink TFI
+
+ if (tbf->is_egprs_enabled()) {
+ /* PU_AckNack_EGPRS = on */
+ bitvec_write_field(dest, wp, 1, 1); // 1: EGPRS
+ write_packet_uplink_ack_egprs(bts, dest, wp, tbf, is_final);
+ } else {
+ /* PU_AckNack_GPRS = on */
+ bitvec_write_field(dest, wp, 0, 1); // 0: GPRS
+ write_packet_uplink_ack_gprs(bts, dest, wp, tbf, is_final);
+ }
+
+ LOGP(DRLCMACUL, LOGL_DEBUG,
+ "Uplink Ack/Nack bit count %d, max %d, message = %s\n",
+ wp, dest->data_len * 8,
+ osmo_hexdump(dest->data, dest->data_len));
+}
+
unsigned Encoding::write_packet_paging_request(bitvec * dest)
{
unsigned wp = 0;